The Wnt proteins were initially implicated in viral carcinogenesis experiments associated with mammary tumors, but since this period investigations focusing on the Wnt pathways, and especially those involving the family member Wnt-1, have been advanced to demonstrate the critical nature of Wnt-1 for the development of the central nervous system (CMS) as well as the potential of Wnt to avert apoptotic injury. As a result, it becomes vital to understand the cellular mechanisms that could foster Wnt-1 as a novel therapeutic target for apoptotic cellular injury in the CNS. We will employ both in vitro and in vivo models in our studies directly relevant to neurodegenerative disease. In vitro studies will consist of oxygen-glucose deprivation and nitric oxide-induced oxidative stress with primary hippocampal neurons used for transient transfections and the neuronal SH-SY5Y cell line used for stable transfections. Rats with middle cerebral artery occlusion and reperfusion injury will compliment this approach to serve as an in vivo model of oxidative stress. In Specific Aim I, we will examine the hypothesis that Wnt-1 signaling is altered by oxidative stress in ischemic brain, neurons, SH-SY5Y cells, and in astrocytes. It is important to consider the effects of Wnt-1 in neuronal cells and astrocytes, since astrocytes may be protective to neurons during oxidative stress. In Specific Aim II, we will investigate the hypothesis that Wnt-1 and its modulation of GSK-3(3 and (3-catenin are required to protect cells against oxidative stress induced apoptosis using overexpression of the Wnt-1 gene as well as targeted gene silencing techniques. In Specific Aim III, we will examine the hypothesis that Wnt-1 protects cells against oxidative stress through the novel activity of protein kinase B (Akt1), modulation of mTOR, Bad, and Bim, and the inhibition of the Forkhead transcription factor FOXOSa. In Specific Aim IV, given that inflammatory microglial activation is dependent upon both PS exposure on injured neurons and intracellular microglial pathways that involve microglial phosphatidylserine receptor (PSR) expression, we will examine the ability of Wnt-1 to modulate neuronal cell pathways that control PS expression and microglial activation as well as the ability of Wnt-1 in microglia to control their activity, proliferation, PSR expression, and cytokine release. With the knowledge that over 23 million people in the United States suffer from CNS disorders composed of only a few neurodegenerative disease entities, such as cerebral ischemic disease and Alzheimer's disease, the studies proposed in this application are directly relevant to the clinical care and treatment of these individuals. Our preliminary results illustrate a unique role for Wnt-1 in its ability to impact upon and protect against oxidative stress induced cell injury and inflammatory cell activation. Through these investigations, we seek to offer innovative avenues to advance therapeutics for diseases of the CNS.